This invention generally relates to a control means for fluid flow and more particularly concerns a fan coil type control wherein a relatively constant fluid flow is maintained through a venturi restrictor by a self-centering metering pin which is movable by variations in the fluid pressure drop thereacross to vary the flow restriction proportionately and thereby maintain constant flow through the control.
Control of fluid flow by means such as a venturi flow meter has been known for over a century yet despite this fact there has remained in the art of flow control a very real need for an economical, accurate, easily constructed and adaptable constant flow control operable under the conditions of low pressure, high flow rates and high temperatures. While there have been many attempts using many different approaches none has proven successful.